On a different wavelength

A safer and more effective way of screening for breast cancer could be on the cards, thanks to research being carried out at the University of Northumbria. Dr David Smith and his team have been investigating the potential of creating holographic images of tumours using microwaves, with promising results. Now the Medical Research Council has provided a £90,000 grant to help create a system that could be used in a medical setting.

There is a big difference in material properties between healthy and malignant tissue at microwave frequencies. So at the interface where the healthy and malignant tissue meet, the microwaves are reflected and scattered. These can be measured by holographic methods, similar to the process used to produce optical holograms.

The scattered microwave signal is combined with a reference signal to produce a set of interference fringes. Unlike a normal hologram, where the eye picks up a 3D image when the original light is shone through it, here a computer and microwaves are used to create the holographic image.

'A number of other groups are using microwaves to create images of breast cancer tumours, but these use pulses of microwaves, much more like radar,' explained Smith. 'Our method is different. We use continuous microwaves rather than a pulse, with a similar power to a television remote control — about a millionth of the level of a microwave oven.' The big advantage of this over a normal photograph is that it gives a 3D image, rather than a flat 2D one.

Another bonus over conventional screening is that it does not use X-rays. 'Microwaves are inherently safe,' said Smith. 'Because they are non-ionising, they cannot cause cancer. As long as you keep the power low, they are safe.'

Smith's group has been working on microwaves for five years, first on microwave antennas and then to detect concealed weapons. Their success with the projects encouraged them to widen the scope of their research, and the Wellcome Trust provided a grant two years ago to see if microwaves could be used to detect simulated tumours.

Breast tumours are an ideal starting point, because the tumour tends to be surrounded by fairly fatty tissue, giving a high level of contrast between malignant and healthy tissue. Their studies so far have used simulated breasts made from paraffin wax, whose material properties are not that different from normal healthy fatty breast tissue, with 'tumours' made from embedded graphite. This material has a high dielectric constant, similar to a tumour.

Smith hopes they will start looking at real tissue within six months. The MRC grant will allow him and a colleague to work with Prof Tom Lennard, head of surgery at Newcastle University's medical school. 'This will ensure we go in the right direction, and see the best way to integrate the technology into medical equipment,' he said.

'We have had encouraging results from our initial "home built" system,' Smith said. We hope that by the end of the year we will be able to pick up good images of different biological tissues. A machine that could be used in clinical trials is maybe three years away.'